Multiple Bonding Between Group-3 Metals and Fe(CO)(3)(-)

Heteronuclear Group 3 metal/iron carbonyl anion complexes ScFe(CO)(3)(-), YFe(CO)(3)(-), and LaFe(CO)(3)(-) are prepared in the gas phase and studied by mass-selective infrared (IR) photodissociation spectroscopy as well as quantum-chemical calculations. All three anion complexes are characterized to have a metal-metal-bonded C-3v equilibrium geometry with all three carbonyl ligands bonded to the iron center and a closed-shell singlet electronic ground state. Bonding analyses reveal that there are multiple bonding interactions between the bare group-3 elements and the Fe(CO)(3)(-) fragment. Besides one covalent electron-sharing metal-metal sigma bond and two dative pi bonds from Fe to the Group 3 metal, there is additional multicenter covalent bonding with the Group 3 atom bonded to Fe and the carbon atoms.